Biological Membranes & Transport

Question 1

Name 3 amphipathic lipid aggregates that form in water

Answer 1

micelle, vesicle, lipid bilayer

Question 2

What is simple diffusion?

Answer 2

Nonpolar compounds move down concentration gradient

Question 3

What is facilitated diffusion?

Answer 3

Molecule moves down its electrochemical gradient Requires transport channel Passive

Question 4

What is primary active transport?

Answer 4

Molecule moves against its electrochemical gradient Requires transport channel ATP is used

Question 5

What is secondary active transport?

Answer 5

Molecules moves against its electrochemical gradient Driven by an ion moving down its electrochemical gradient Requires transport channel Ion and molecule move in the same direction

Question 6

What is an ion channel?

Answer 6

Molecule moves down its electrochemical gradient May be gated by a ligand or ion Requires transport channel

Question 7

What is ionophore-mediated ion transport?

Answer 7

Molecule moves down its electrochemical gradient Ionophore picks up ion outside the cell, moves through membrane, drops ion off inside the cell, and can then repeat the cycle

Question 8

Name the components of the phospholipid bilayer

Answer 8

Hydrophilic head (polar) and hydrophobic tail (nonpolar)

Question 9

Why is cholesterol an important in the cell membrane?

Answer 9

Gives rigidity and intregrity to the membrate Has OH which allows it to be amphipathic It is a precursor of hormones

Question 10

What causes archaea to have an unusual cell membrane?

Answer 10

Ether bond Causes lipid properties to withstand extreme temperatures

Question 11

Permeability of phospholipid bilayer

Answer 11

From low permeability to high permeability: Ion (impermeable to phospholipid bilayer) Glucose, sucrose/ large uncharged polar molecules (impermeable) H2O, indole, glycerole/ small uncharged polar molecules (semipermeable) O2, CO2, N2/ hydrophobic molecules (freely permeable)

Question 12

What is a peripheral protein?

Answer 12

A protein that is attached to the outside of the lipid bilayer.

Question 13

What is an integral protein?

Answer 13

A protein that is free floating in the lipid bilayer Exposed ends are hydrophilic Strongest connection; must have detergent to remove from membrane Carboxy-terminis inside, amino-terminis outside

Question 14

Explain the asymetric distribution of phospholipids in plasma membrane

Answer 14

Phospholipids that are high inside will be low outside, and vice versa

Question 15

Explain the translipid deposition of glycophorin in an electrocyte

Answer 15

Carboxyl-terminis end inside Amino-terminis end outside

Question 16

How do integral proteins embed into the phospholipid bilayer?

Answer 16

It has hydrophobic amino acids in its structure

Question 17

How do lipid-linked membrane proteins attach to the phospholipid bilayer?

Answer 17

There is a protein component and a lipid component. Lipid component anchors the complex into the phospholipid bilayer by attaching to the hydrophobic tails

Question 18

What is uniport?

Answer 18

Single molecule moves one direction across membrane Ex. glucose

Question 19

What is symport?

Answer 19

Type of cotransport Two different molecules move in the same direction at the same time across the membrane Ex. glucose and Na

Question 20

What is antiport?

Answer 20

Type of cotransport Two different molecules move in opposite directions at the same time across the membrane Ex. Na/K ATPase

Question 21

Describe uncatalyzed transbilayer (“flip-flop”) diffusion

Answer 21

Lipid moves from one side of the lipid bilayer to the other (ex. inside border to the outside border) Occurs very slow

Question 22

Describe uncatalyzed lateral diffusion

Answer 22

Lipid moves up or down the lipid bilayer on the same side Occurs very fast

Question 23

Name the 3 enzymes involved in catalyzed transbilayer translocations

Answer 23

Flippase Floppase Scramblase

Question 24

Name this membrane lipid and its class

Answer 24

Glycerophospholipid from the phospholipid class

Question 25

Name this membrane lipid and its class

Answer 25

Sphingolipid from the phospholipid and glycolipid classes

Question 26

Name this membrane lipid and its class

Answer 26

Cholesterol from the sterol class

Question 27

What are lipid rafts?

Answer 27

specialized membrane microdomains that compartmentalize cellular processes

Question 28

What are characteristics of caveolar membranes?

Answer 28

• they are membrane microdomains that have caveolin as the prinicpal component
• Caveolins may act as scaffolding proteins within caveolar membranes by compartmentalizing and concentrating signaling molecules
• receptor-independent endocytosis

Question 29

How does simple diffusion without a transporter compare with diffusion with a transporter, in relation to entropy?

Answer 29

• simple diffusion without a tranporter will cause an increase in entropy
• diffusion without a transporter will cause a decrease in entropy

Question 30

Describe the enzymatic action of carbonic anhydrase on carbon dioxide that occurs inside RBCs

Answer 30

• in respiring tissues, CO2 enters the RBC, where it is converted to carbonic acid and bicarbonate via carbonic anhydrase; bicarbonate is released into plasma
• in the lungs, bicarbonate and carbonic acid are converted to CO2 via carbonic anhydrase; CO2 is exhaled